A technique using aqueous fluorinated resin compositions as resins for weather-resistant paints is heretofore known; however, such paints are generally inferior to solvent-based crosslinking type paints with regard to water resistance, solvent resistance, soil-resistance, hardness, etc. To overcome this drawback, the development of aqueous crosslinking type fluorinated resins has been under taken, though not yet completed. Examples of copolymers of crosslinking monomers with chlorotrifluoroethylene, tetrafluoroethylene or hexafluoropropylene are disclosed in U.S. Pat. No. 5,548,019 and Japanese Unexamined Patent Publication No. 1995-324180. However, these are copolymers with non-fluoroolefin monomers, having a relatively large amount of added non-fluoroolefin monomers (about 50 mol %), resulting in resins and coated films of unfavorable quality in terms of durability and weather resistance.
It is known that compositions formed from polyvinylidene fluorides and acrylic polymers having crosslinkable groups can be obtained using techniques disclosed in Japanese Unexamined Patent Publication No. 1995-268163 and Japanese Unexamined Patent Publication No. 2001-72725. However, these compositions exhibit insufficient water resistance, solvent resistance, soil-resistance and hardness because the fluorinated resin does not contain a crosslinkable group and there is thus no chemical bond between the fluorinated resin and the acrylic resin. Presumably, the coated film has a low crosslinking density as a whole and the compatibility between the fluorinated resin and the acrylic resin subjected to crosslinking reaction is low.
The present invention aims at providing an aqueous emulsion resin composition having excellent water resistance, solvent resistance, soil-resistance and hardness.